In spite of extensive medical research and numerous advances, cancer remains the second leading cause of death in the United States. Breast cancer is the most common cause of cancer deaths in women. While the traditional modes of therapy, such as surgery, radiotherapy and chemotherapy, are widely used and are in many instances successful, there is still a significant failure rate, especially for solid tumors. The still existing high death rate from cancers such as breast compels the need for alternative modes of therapy.
The immunotherapy of human cancer using tumor cells or tumor-derived vaccines has been disappointing for several reasons. It has been consistently difficult to obtain large quantities or purified tumor-associated antigens which are often chemically ill-defined and difficult to purify. In addition, there remains the problem of immunobiological response potential against tumor antigens, or in other words, the question of whether a cancer patient can effectively mount an immune response against his or her tumor. Tumor-associated antigens (TAA) are often a part of “self” and usually evoke a very poor immune response in a tumor-bearing host due to tolerance to the antigens, such as T cell-mediated suppression. Moreover, cancer patients tend to be immunosuppressed, and only respond to certain T-dependent antigens.
Immunobiologists have learned that a poor antigen (in terms of eliciting an immune response) can be turned into a strong antigen by changing the molecular environment. Changes of hapten carrier allow T cell helper cells to become active, making the overall immune response stronger. Thus, changing the carrier can also turn a tolerogenic antigen into an effective antigen. McBridge et al. (1986) Br. J. Cancer 53:707. Often the immunological status of a cancer patient is suppressed such that the patient is only able to respond to certain T-dependent antigens and not to other antigen forms. From these considerations, it would make sense to introduce molecular changes into the tumor associated antigens before using them as vaccines. Unfortunately, this is impossible to accomplish for most tumor antigens, because they are not well defined and are very hard to purify.
The network hypothesis of Lindemann ((1973) Ann. Immunol. 124:171-184) and Jerne ((1974) Ann. Immunol. 125:373-389) offers an elegant approach to transform epitope structures into idiotypic determinants expressed on the surface of antibodies. According to the network concept, immunization with a given tumor-associated antigen will generate production of antibodies against this tumor-associated antigen, termed Ab1; this Ab1 is then used to generate a series of anti-idiotype antibodies against the Ab1, termed Ab2. Some of these Ab2 molecules can effectively mimic the three-dimensional structure of the tumor-associated antigen identified by the Ab1. These particular anti-idiotypes called Ab2β fit into the paratopes of Ab1, and express the internal image of the tumor-associated antigen. The Ab2β can induce specific immune responses similar to those induced by the original tumor-associated antigen and can, therefore, be used as surrogate tumor-associated antigens. Immunization with Ab2β can lead to the generation of anti-anti-idiotype antibodies (Ab3) that recognize the corresponding original tumor-associated antigen identified by Ab1. Because of this Ab1-like reactivity, the Ab3 is also called Ab1′ to indicate that it might differ in its other idiotopes from Ab1.
A potentially promising approach to cancer treatment is immunotherapy employing anti-idiotype antibodies. In this form of therapy, an antibody mimicking an epitope of a tumor-associated protein is administered in an effort to stimulate the patient's immune system against the tumor, via the tumor-associated protein. WO 91/11465 describes methods of stimulating an immune response in a human against malignant cells or an infectious agent using primate anti-idiotype antibodies. However, not all anti-idiotype antibodies can be used in therapeutic regimens against tumors. First, only a fraction of antibodies raised against an Ab1 are limited in their reactivity to the paratope of Ab1 (i.e., are non-reactive against features shared with other potential antibodies in the host). Second, anti-idiotype antibodies are not necessarily immunogenic. Third, even if an anti-idiotype elicits an immune response, only a fraction of these immunogenic anti-idiotypes elicit an immune response against the tumor antigen and not against other antigens with less specificity. Moreover, since different cancers have widely varying molecular and clinical characteristics, it has been suggested that anti-idiotype therapy should be evaluated on a case by case basis, in terms of tumor origin and antigens express.
Anti-Id monoclonal antibodies structurally resembling tumor-associated antigens have been used as antigen substitutes in cancer patients. Herlyn et al. (1987) PNAS 84:8055-8059; Mittleman et al. (1992) PNAS 89:466-470; Chatterjee et al. (1993) Ann. N.Y. Acad. Sci 690:376-377. It has been proposed that the anti-Id provides a partial analog of the tumor-associated antigen in an immunogenic context.
Human milk fat globules (HMFG) are milk fat globules secreted into breast milk by the breast epithelial cell, and are composed of fat droplets enveloped by plasma membrane. As such, HMFG is a rich source of epithelial membrane-associated antigens. One antigen component of HMFG is a high molecular weight, membrane-associated mucin that is associated with breast and other cancers such as ovarian, lung, and pancreas. The mucin contains a protein with known amino acid sequences derived from the cDNA. Semipurified HMFG is available in small quantities from several sources and can be used in serological assays. Peterson et al. (1990) Hybridoma 9:221-235. However, HMFG is extremely difficult to isolate and purify, and purified HMFG is not available for patient immunization or animal studies. Further, inasmuch as some of the epitopes on HMFG are shared by normal tissues, specifically by nonpenetrating glycoproteins, immunization with intact HMFG molecule might trigger potentially harmful autoimmune reactions. An immune reaction against a tumor-associated epitope, on the other hand, would be much more desirable.
A series of murine monoclonal antibodies (mAbs) that recognize components of HMFG have been described that are primarily associated with human breast carcinomas and not with most normal tissues. Chatterjee et al. (1993) Ann. N.Y. Acad. Sci. 690:376-377; Ceriani et al. (1983) Somatic Cell Genet. 9:415-427. Among these mAbs, MC-10 (BrE-1) is the most restricted and specific, reacting with a large molecular weight (MW, 400,000) mucin-like protein present at high density and on >80% breast cancer cells and minimally expressed on a few normal tissues, such as the epithelial lining of lung and kidney tubules. Ceriani et al. (1983); Ceriani et al. (1990) Antibody Immunoconjugates and Radiopharmaceuticals 3:181-198.
Recurrent breast cancer is not curable by standard therapies. Thus, new therapeutic approaches for this disease are needed. The present invention overcomes the deficiencies in the prior art by providing a monoclonal anti-idiotype antibody (11D10) as an antigen (Ag) that elicits an immune response against HMFG in non-human primates, which may be useful for treating anti-tumor immunity in patients with advanced HMFG-associated cancer (such as breast cancer).
All publications cited herein are hereby incorporated by reference in their entirety.